Methods for making laminated member for circuit board, making circuit board and laminating flexible film

ABSTRACT

The present invention relates to a circuit board including a flexible film provided with an extremely fine circuit pattern, a laminated member for a circuit board, and a method for making a laminated member for a circuit board with excellent productivity. A circuit board of the present invention includes a flexible film and a circuit pattern composed of a metal provided on the flexible film, and dimensional change rate of the circuit pattern is within ±0.01%. A laminated member for a circuit board of the present invention includes a reinforcing plate, a self-stick, removable organic layer, a flexible film, and a circuit pattern composed of a metal laminated in that order.

This application is a divisional of U.S. patent application Ser. No.10/450,415, which is a 371 of international application PCT/JP02/07242filed Jul. 17, 2002, and claims priority based on Japanese patentapplication Nos. 2001-219295 and 2002-27763 filed Jul. 19, 2001, andFeb. 5, 2002, respectively, which are incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a circuit board including a flexiblefilm provided with an extremely fine circuit pattern, a laminated memberfor a circuit board, and a method for making a laminated member for acircuit board with excellent productivity.

BACKGROUND ART

With the reduction in size and weight of electronic products, higherprecision in patterning of printed circuit boards has been required.Since flexible film substrates can be bent, which enablesthree-dimensional wiring, they are suitable for reduction in size ofelectronic products. Therefore, the demand for flexible film substratesis increasing. With respect to tape automated bonding (TAB) techniqueswhich are used for connecting ICs to liquid crystal display panels, bythe roll-to-roll process with a relatively narrow polyimide filmsubstrate, it is possible to obtain an excellent fine-pattern as a resinsubstrate. However, the development of micro-fabrication with apolyimide film substrate is substantially reaching its limits. In orderto evaluate accuracy of a miniaturized pattern, an index represented bythe line width and the space between lines, and an index represented bythe position of the pattern on the substrate are used. With respect tothe line width and the space between lines, further miniaturization maybe possible. The latter index, i.e., dimensional change rate, relates tothe alignment accuracy between a circuit board pattern and electrodepads when the circuit board and electronic components, such as ICs, areconnected to each other, and as the pitch between electrode pads in anIC is further narrowed and the number of electrode pads in an IC isincreased, it becomes difficult to meet the required accuracy. That is,when an IC having more than 400 to 1,000 electrode pads is connected toa circuit pattern, extremely low dimensional change rate is required toalign all the electrode pads in an IC with fine electrode pads with apitch of 60 μm or less, preferably 50 μm or less, of the circuitpattern.

In terms of dimensional change rate, it is, in particular, difficult toimprove the fabrication of flexible film substrates. In the circuitboard fabrication, heat treatment processes, such as drying and curing,and wet processes, such as etching and development, are performed, andthe flexible film is repeatedly subjected to expansion and shrinkage.The hysteresis during the fabrication processes causes distortion of thecircuit pattern on the substrate. In the case when a plurality ofprocesses require alignment, if expansion and shrinkage occur duringsuch processes, positioning error occurs between patterns formed. Thedistortion of the flexible film due to expansion and shrinkage moregreatly affects a flexible printing circuit (FPC) in which a substratewith a relatively large area is treated. Additionally, positioning erroris also caused by external forces, such as tension and torsion, and, inparticular, when a thin substrate is used to increase flexibility,adequate care must be taken. Since the flexible film substrate expandsand shrinks due to humidity and temperature even after the circuitformation, it is absolutely necessary to control temperature andhumidity of the circuit board prior to the IC connection. Even whenmoisture proof packaging is used, the production cost is increased, itis difficult to achieve complete moisture proofing, and the guaranteeperiod is limited. Under the circumstances, the upper limit ofdimensional change rate of the circuit pattern formed on a flexible filmhas been considered to be approximately ±0.015 to ±0.030%, and it isbecoming difficult to cope with further narrowing of the pitch andincrease in the number of electrode pads in an IC.

DISCLOSURE OF INVENTION

In view of the problems associated with the conventional techniquesdescribed above, the present inventors have conducted thorough researchon an extremely fine flexible film circuit board and a method for makinga laminated member for a circuit board with excellent productivity, andhave found that such problems are solved by attaching a flexible film toa reinforcing plate having excellent dimensional stability with aself-stick, removable organic layer therebetween, followed byprocessing, and also have searched into specific preferred embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view which schematically shows a central part of alaminator 1 in accordance with the present invention.

FIG. 2 is a sectional view taken along the line X-X of FIG. 1.

FIGS. 3(a) to 3(f) are front views which schematically show steps in alamination method in accordance with the present invention.

REFERENCE NUMERALS

-   1 laminator-   2 film holding sheet-   3 stage-   4 flexible film-   6 reinforcing plate-   7 self-stick, removable organic layer-   8 squeegee-   9 base-   10 frame-   12 electrostatic charging device-   14 column-   16 bracket-   18 motor-   20 ball screw-   22 bracket-   24 guide-   26 nut-   28 squeegee support-   32 a, 32 b bearing-   34 rotary cylinder-   36 a, 36 b guide-   38 rail-   40 moving body-   42 stator-   43 linear motor-   44 a, 44 b support-   46 linear cylinder

BEST MODE FOR CARRYING OUT THE INVENTION

In one aspect of the present invention, a circuit board includes aflexible film and a circuit pattern composed of a metal provided on atleast one surface of the flexible film, and dimensional change rate ofthe circuit pattern is within ±0.01%.

The flexible film of the present invention is a plastic film, and it isimportant that the plastic film has heat resistance sufficient forthermal processes in the circuit-pattern-forming step and in theelectronic-component-mounting step. Examples of plastic films usedinclude polycarbonate, polyether sulfide, polyethylene terephthalate,polyethylene naphthalate, polyphenylene sulfide, polyimide, polyamide,and liquid crystal polymer films. Among these, a polyimide film ispreferably used because of its excellent heat resistance and excellentresistance to chemicals. A liquid crystal polymer is preferably usedbecause of its excellent electrical characteristics, such as lowdielectric loss. A flexible glass-fiber reinforced resin sheet may alsobe used.

Examples of resins of glass-fiber reinforced resin sheet include epoxyresins, polyphenylene sulfide resins, polyphenylene ether resins,maleimide (co)polymer resins, polyamide resins, and polyimide resins.The thickness of the flexible film is preferably small in view ofreduction in weight and size of the electronic apparatuses and in orderto form fine via-holes, while the thickness is preferably large in orderto ensure mechanical strength and to maintain flatness. Therefore, thethickness of the flexible film is preferably in the range of 7.5 to 125μm.

A circuit pattern composed of a metal is provided on the flexible film.The metal layer may be formed by laminating a metallic foil, such as acopper foil, using an adhesive layer, by sputtering, by plating, or bycombining these. Alternatively, a raw material resin or its precursorfor the flexible film may be applied to a metallic foil, such as acopper foil, followed by drying and curing to form a flexible filmprovided with a metal layer. As the metal layer, any highly conductivemetal can be used, and for example, gold, silver, or aluminum may beused. As the method for forming the circuit pattern composed of themetal, a full additive process, a semi-additive process, or asubtractive process may be used.

The full additive process will be described below. A catalyst, such aspalladium, nickel, or chromium, is applied to the surface on which acircuit pattern is to be formed, followed by drying. Herein, thecatalyst does not act as the nucleus for plating growth as it is.However, after the catalyst is activated, it acts as the nucleus forplating growth. A photoresist is then applied thereto by a spin coater,blade coater, roll coater, bar coater, or die coater, or by screenprinting, followed by drying. The photoresist is exposed through aphotomask with a predetermined pattern to form a photoresist layer inthe sections in which the plating film is not required. The exposedphotoresist is developed. Catalyst is then activated, and the polyimidefilm is dipped in an electroless plating solution composed of coppersulfate and formaldehyde to form a copper-plating layer with a thicknessof 2 to 20 μm. The photoresist layer is removed as required. A circuitpattern is thereby obtained.

The semi-additive process will be described below. An underlayer isdeposited on a surface on which a metal layer is to be formed bysputtering of chromium, nickel, copper, or an alloy of these metals. Thethickness of the underlayer is in the range of 1 to 1,000 nm. It iseffective in securing sufficient conductivity for subsequentelectroplating, in improving adhesion of the metal layer, and inpreventing pinhole defects to deposit a copper layer by sputteringfurther on the underlayer at a thickness of 50 to 3,000 nm. Before theunderlayer is formed, in order to improve adhesion, the surface of thepolyimide film may be subjected to plasma treatment, reverse sputtering,primer layer application, or adhesive layer application as appropriate.A photoresist is applied to the underlayer, followed by drying. Thephotoresist is exposed through a photomask with a predetermined patternto form a photoresist layer in the sections in which the plating film isnot required. The exposed photoresist is developed. Electroplating isthen performed using the underlayer as an electrode. As theelectroplating solution, a copper sulfate plating solution, a coppercyanide plating solution, a copper pyrophosphate plating solution, orthe like is used. A copper-plating layer is formed at a thickness of 2to 20 μm, and optionally, plating with gold, nickel, tin, or the like isfurther performed. The photoresist is removed, and the underlayer isremoved by slight etching. A circuit pattern is thereby obtained.

The subtractive process will be described below. First, a uniform metallayer is formed on a flexible film. In order to form the uniform metallayer, a metallic foil, such as a copper foil, may be laminated to aflexible film with an adhesive layer, or the metal layer may be formedon a flexible film by sputtering, plating, or a combination of these.Alternatively, a raw material resin or its precursor for the flexiblefilm may be applied to a metallic foil, such as a copper foil, followedby drying and curing to form a flexible film provided with a metallayer. Next, a photoresist is applied to the metal layer, followed bydrying. The photoresist is exposed through a photomask with apredetermined pattern to form a resist layer in the sections in whichthe metal film is required. The exposed photoresist is developed. Afteretching the metal layer, the photoresist layer is removed, and a circuitpattern is thereby obtained.

It is important that dimensional change rate of the circuit pattern ofthe present invention is within ±0.01% in order to cope with furthernarrowing of the pitch and increase in the number of electrode pads inan IC, and more preferably, dimensional change rate is within ±0.005.

In another aspect of the present invention, a laminated member for acircuit board includes a reinforcing plate, a self-stick, removableorganic layer, a flexible film, and a circuit pattern composed of ametal laminated in that order.

Examples of materials for a substrate used as the reinforcing plateinclude inorganic glasses, such as soda-lime glass, borosilicateglasses, and silica glass; ceramics, such as alumina, silicon nitride,and zirconia; metals, such as stainless steels, Invar alloys, andtitanium; and glass-fiber reinforced resins. All of these materials arepreferably used because of their small coefficient of thermal expansionand small coefficient of hygroscopic expansion. Inorganic glasses aremore preferably used because of their excellent heat resistance andresistance to chemicals in the circuit-pattern-forming step, becauselarge-area substrates with satisfactory surface smoothness are easilyobtained, because plastic deformation does not easily occur, or becauseparticles are not easily generated by collision during transportation.Among them, a borosilicate glass represented by aluminoborosilicateglass is most preferably used because of its high modulus of elasticityand small coefficient of thermal expansion.

When a metal or a glass-fiber reinforced resin is used as thereinforcing plate, although manufacturing may be performed in the formof a long web, in other words, performed by a roll-to-roll process, inorder to easily obtain low dimensional change rate, the circuit board ofthe present invention is preferably manufactured by sheet processing.The sheet processing is also preferable because high alignment accuracyis easily secured by optical position detection, a movable stage, etc.,in the electronic-component-mounting step. Herein, the sheet processingmeans that, instead of a long web, individual sheets are handled.

When a glass substrate is used as the reinforcing plate, if the glasssubstrate has a small Young's modulus or the glass substrate is thin,since warpage and torsion are increased by the expansion and shrinkageof the flexible film, the glass substrate may be cracked whenvacuum-sucked on a flat stage. Additionally, since the flexible film isdeformed by vacuum suction/release, it tends to be difficult to maintainlow dimensional change rate. On the other hand, if the glass substrateis thick, flatness may be degraded due to nonuniform thickness,resulting in a decrease in exposure accuracy. Additionally, handlingload by a robot or the like increases and it becomes difficult totransfer substrates quickly, resulting in a decrease in the productivityand an increase in transportation cost. For the reasons described above,with respect to the glass substrate used as a reinforcing plate (whenthe sheet processing is used), the product of the Young's modulus(kg/mm²) and the cube of the thickness (mm) is preferably 850 to 860,000kg·mm, more preferably 1,500 to 190,000 kg·mm, and most preferably 2,400to 110,000 kg·mm.

When a metal substrate is used as the reinforcing plate, if the metalsubstrate has a small Young's modulus or the metal substrate is thin,since warpage and torsion are increased by the expansion and shrinkageof the flexible film, it becomes impossible to vacuum-suck the substrateon a flat stage. Since the flexible film is deformed due to the warpageand torsion of the metal substrate, it becomes difficult to secure lowdimensional change rate. Additionally, if creasing occurs, the productis considered to be a defective product. On the other hand, if the metalsubstrate is thick, flatness may be degraded due to nonuniformthickness, resulting in a decrease in exposure accuracy. Additionally,handling load by a robot or the like increases and it becomes difficultto transfer substrates quickly, resulting in a decrease in theproductivity and an increase in transportation cost. For the reasonsdescribed above, with respect to the metal substrate used as areinforcing plate, the product of the Young's modulus (kg/mm²) and thecube of the thickness (mm) is preferably 2 to 162,560 kg·mm, morepreferably 10 to 30,000 kg·mm, and most preferably 15 to 20,500 kg·mm.

The self-stick, removable organic layer used in the present invention iscomposed of an adhesive or pressure-sensitive adhesive, and any adhesivethrough which the flexible film can be attached to the reinforcing plateand from which the flexible film can be detached after processing may beused. As the adhesive or pressure-sensitive adhesive, for example, aself-stick, removable acrylic or urethane adhesive may be used. Theadhesion of the adhesive is preferably in the weak adhesion range sothat satisfactory adhesion is exhibited when the flexible film isprocessed and detachment is easily performed without causing distortionof the flexible film substrate.

A silicone resin film may be used as a release agent in the presentinvention. A silicone resin layer with tackiness may also be used as theself-stick, removable organic layer in the present invention. An epoxyresin layer with tackiness may also be used as the self-stick, removableorganic layer.

An adhesive whose adhesion decreases in the low-temperature region, anadhesive whose adhesion is decreased by ultraviolet irradiation, or anadhesive whose adhesion is decreased by heat treatment may also bepreferably used. Among them, the adhesive in which adhesion is decreasedby ultraviolet irradiation is more preferably used because a change inadhesion is large before and after ultraviolet irradiation, and bycrosslinking the adhesive by ultraviolet irradiation before electroniccomponents are bonded to the substrate with high-temperature andhigh-pressure, it is possible to suppress softening of the adhesive dueto temperature and deformation due to pressure. In order to ensureresistance to chemicals and heat resistance in thecircuit-pattern-forming-step, crosslinking by ultraviolet irradiation ispreferably performed before the wet process and/or heating process inthe circuit-pattern-forming-step. Examples of the adhesive in whichadhesion and tackiness are decreased by ultraviolet irradiation includea two-part acrylic adhesive. Examples of the adhesive in which adhesionand tackiness decrease in the low-temperature region include an acrylicadhesive which is reversibly transformed between the crystalline stateand the non-crystalline state.

In the present invention, the preferable adhesion of the self-stick,removable organic layer is measured by the straight angle peel strengthwhen a flexible film with a width of 1 cm attached to a reinforcingplate with the self-stick, removable adhesive is peeled off. The peelrate for measuring the adhesion is 300 mm/min. Herein, the weak adhesionrange refers to a range of 0.1 to 100 g/cm when adhesion is measuredunder the conditions described above.

If the peel strength with which the flexible film is peeled off theself-stick, removable organic layer is too small, the flexible film maybe detached during the formation of the circuit pattern. On the otherhand, if the peel strength with which the flexile film is peeled off theself-stick, removable organic layer is too large, the flexible film isdeformed during peeling, resulting in an increase in dimensional changerate. If the adhesive strength is too large, curling of the flexiblefilm may also occur, which causes problems in the steps subsequent topeeling. The deformation and curling also depend on the Young's modulusand thickness of the flexible film. By controlling these parameterswithin specific ranges, the flexible film is not detached in thefabrication process, and the deformation and curling of the flexiblefilm due to peeling can be prevented. That is, the product of A, B, andC is preferably in the range of 4.3×10⁻⁶ to 4.3×10⁻³, more preferably inthe range of 8.6×10⁻⁶ to 8.6×10⁻⁴, and most preferably in the range of2.15×10⁻⁵ to 5.16×10⁻⁴, where A (g/cm) is the peel strength, B (μm⁻¹) isthe reciprocal of the thickness of the flexible film, and C (mm²/kg) isthe reciprocal of the Young's modulus of the flexible film.

In order to apply the self-stick, removable organic layer and aphotoresist to the substrate, a wet coating method is used. Examples ofwet coating apparatuses used include spin coaters, reverse coaters, barcoaters, blade coaters, roll coaters, die coaters, screen printers, dipcoaters, and spray coaters. When the self-stick, removable organic layeris directly applied to individual reinforcing plates and a photoresistfor forming the circuit board is directly applied to individual flexiblefilm sheet substrates, a die coater is preferably used. That is,although a spin coater is usually used in the wet coating method forindividual sheet substrates, since the thickness of coated layer iscontrolled by the balance between the centrifugal force due to the highrevolution of the substrate and the adsorbability to the substrate, theutilization ratio of the coating solution is 10% or less, thus beingineffective. Additionally, since the centrifugal force is not applied tothe center of rotation, although it depends on the types of the coatingsolution used, it may be difficult to apply a thixotropic coatingsolution or a coating solution with high viscosity uniformly to thesubstrate. With respect to a reverse coater, bar coater, or bladecoater, in order to obtain stable coating thickness, a coating length ofseveral tens of centimeters to several meters or more is required afterdischarging of the coating solution starts, and therefore, such a coatermust be used carefully when individual sheet substrates are coated. Withrespect to a roll coater, screen printer, dip coater, or spray coater,it is difficult to obtain high accuracy in coating thickness, and thetolerance for the flow characteristic of the coating solution is narrow.With respect to a roll coater, dip coater, or a spray coater, it isdifficult to form a thick film by coating. With respect to a die coater,by combining a periodically driven metering pump, a mechanism forrelatively moving a substrate and a coating head, and a system forcomprehensively controlling the metering pump, the substrate, and thecoating head, it is possible to suppress the nonuniformity of thicknessin the moving direction at the coating start section and the coating endsection in the range of several millimeters to several tens ofmillimeters when individual sheet substrates are coated. Examples ofperiodically driven metering pumps are gear pumps and piston pumps.Since the self-stick, removable organic layer generally has a higherviscosity than that of a photoresist, a die coater is preferably used.

The self-stick, removable organic layer may be directly applied to thereinforcing plate, or the self-stick, removable organic layer may beapplied to another base, such as a long web, and then transferred to thereinforcing plate. When the transferring method is employed, although aportion with uniform thickness only can be used, the number of steps isincreased, or another base for transferring is required.

Alternatively, the self-stick, removable organic layer may be applied tothe flexible film used as the substrate of the circuit board, and thenlaminated to the reinforcing plate.

Peeling may be performed either at the interface between the reinforcingplate and the self-stick, removable organic layer or at the interfacebetween the self-stick, removable organic layer and the flexible film.Peeling is preferably performed at the interface between the self-stick,removable organic layer and the flexible film because the step ofremoving the self-stick, removable organic layer adhering to theflexible film after peeling of the self-stick, removable organic layercan be omitted. Preferably, an auxiliary adhesive layer is providedbetween the reinforcing plate and the self-stick, removable organiclayer. Consequently, the self-stick, removable organic layer and theflexible film can be detached at the interface therebetween morereliably.

Preferably, the auxiliary adhesive agent has strong adhesion with thereinforcing plate and the self-stick, removable organic layer, andpreferred examples thereof include silane, organotitanium, andorganophosphorus auxiliary adhesive agents. Examples of silane auxiliaryadhesive agents include halogen silanes, alkoxy silanes, and acetoxysilanes, and examples of organotitanium auxiliary adhesive agentsinclude titanium esters, titanium acylates, and titanium chelates.Examples of organophosphorus auxiliary adhesive agents includemono-alkyl phosphates, alkyl phosphonates, and dialkyl phosphites.Preferably, a silane auxiliary adhesive agent is employed because it canbe easily and smoothly applied to the reinforcing plate and it isinexpensive. When the reinforcing plate is composed of glass, an alkoxysilane represented by formula (I) below is particularly preferablebecause it has satisfactory wettability with glass and quickly reactswith glass to form a strong bond.

wherein, each of R¹ and R² is a monovalent alkyl group, R¹ and R² beingthe same or different, each of R³ and R⁴ is an alkyl group having 1 to 5carbon atoms, R³ and R⁴ being the same or different, and each of a, b,and c is an integer of 0, 1, 2, or 3, the relationship a+b+c=1 to 3being satisfied.

Specific examples of the alkoxy silane represented by formula (I)include, but are not limited to, vinyltrimethoxy silane, vinyltriethoxysilane, vinyltris(β-methoxyethoxy)silane,β-(3,4-epoxycyclohexyl)ethyltrimethoxy silane,γ-glycidoxypropyltrimethoxy silane, γ-glycidoxypropylmethyldiethoxysilane, γ-glycidoxypropyltriethoxy silane,γ-methacryloxypropylmethyldiethoxy silane,γ-methacryloxypropyltrimethoxy silane,γ-methacryloxypropylmethyldiethoxy silane, γ-methacryloxypropyltriethoxysilane, N-β(aminoethyl)γ-aminopropylmethyldimethoxy silane,N-β(aminoethyl)γ-aminopropyltrimethoxy silane,N-β(aminoethyl)γ-aminopropyltriethoxy silane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxy silane, N-phenyl-γ-aminopropyltrimethoxysilane, γ-chloropropyltrimethoxy silane, γ-mercaptopropyltrimethoxysilane, and phenyltriethoxy silane.

In the present invention, the auxiliary adhesive layer may be formed byany method, and for example, by a method in which an auxiliary adhesiveagent is applied alone or as a solution obtained by dissolving theauxiliary adhesive agent in a solvent, followed by drying. Specificexamples of the solvent used include acetone, methyl ethyl ketone,methyl isobutyl ketone, cyclohexanone, 2-heptanone, ethyl acetate, butylacetate, hexyl acetate, butyl propionate, methanol, ethanol, isopropylalcohol, ethylene glycol, propylene glycol, tetrahydrofuran,1,3-dioxane, 1,4-dioxane, heptane, octane, nonane, decane,γ-butyrolactone, δ-decanolactone, benzene, toluene, xylene,1,2-dichloroethane, chloroform, chlorobenzene, 1,2-dimethoxyethane,diethylene glycol dimethyl ether, diethylene glycol ethyl methyl ether,diethylene glycol diethyl ether, N,N-dimethylformamide,N,N-dimethylacetamide, dimethyl sulfoxide, N-methyl-2-pyrrolidone, andsulfolane.

If the auxiliary adhesive layer is too thin, satisfactory adhesion isnot easily exhibited, and if the auxiliary adhesive layer is too thick,cracks and peeling may occur. Therefore, the thickness of the auxiliaryadhesive layer is preferably 2 nm to 5 μm, and more preferably 5 nm to 1μm.

In the present invention, in order to improve adhesion between thereinforcing plate and the self-stick, removable organic layer, roughnessmay be formed on the reinforcing plate. If roughness is formed on thesurface of the reinforcing plate to which the flexible film islaminated, the removable organic substance enters the roughness, andadhesion with the reinforcing plate is increased by the anchoringeffect. Surface roughness may be formed by sand blasting, chemicaletching, or a method in which a rough surface layer is formed on thesurface of the reinforcing plate, but the method is not limited thereto.In chemical etching, the reinforcing plate is immersed in an acid oralkaline aqueous solution so that the surface is etched, thus formingroughness. In particular, when the reinforcing plate is a glasssubstrate, since the reinforcing plate has high resistance to chemicals,high-concentration hydrogen fluoride or sodium hydroxide is preferablyused. Although the material for beads used in sand blasting is notparticularly limited, since the reinforcing plate is generally composedof a hard material, a glass, a ceramic, a metal, or the like ispreferably used. If the particle size of the beads used in sand blastingis too small, kinetic energy that is sufficient for forming roughnesscannot be obtained, and if it is too large, dense roughness cannot beobtained. Therefore, the particle size is preferably 10 μm to 1 mm. Asthe method in which a rough surface layer is formed on the surface ofthe reinforcing plate, for example, a film is formed on the reinforcingplate by mixing a blowing agent into a major ingredient of the film, andthe blowing agent is then expanded. In another method, a layer is formedby mixing additives which are decomposed by heat, ultraviolet light, orthe like into a major ingredient of the layer, and the additives arethen removed by decomposition to form roughness.

If the size of the roughness formed as described above is too small,sufficient adhesion cannot be obtained, and if it is too large, flatnessis degraded. Therefore, the average surface roughness is preferably inthe range of 100 nm to 5 μm, and more preferably in the range of 1 μm to3 μm.

In order to improve the adhesion between the reinforcing plate and theself-stick, removable organic layer, the method for providing anauxiliary adhesive layer and the method for forming a rough surface onthe reinforcing plate may be used alone or in combination.

In the present invention, before the flexible film is laminated to thereinforcing plate, preferably, a circuit pattern and alignment marks areformed on one of the surfaces of the flexible film, i.e., on thelaminating surface. When the reinforcing plate is transparent, thealignment marks may be read through the reinforcing plate or through theflexible film. When a metal layer is formed on the opposite surface tothe laminating surface of the flexible film, the alignment marks arepreferably read through the reinforcing plate because reading can beperformed regardless of the pattern of the metal layer. The alignmentmarks may also be used for the alignment when the flexible film islaminated to the reinforcing plate. The shape of the alignment marks isnot particularly limited, and any shape commonly used in aligners may bepreferably used.

The circuit pattern formed on the opposite surface to the laminatingsurface after the lamination to the reinforcing plate has a pitch of 60μm or less, and more preferably 50 μm or less, which is a pattern withparticularly high precision. In contrast, the pattern formed on thelaminating surface to the reinforcing plate is mainly used forinput/output terminals to the printed circuit board, their peripherallines, power lines and ground lines, and in some cases, precision ashigh as that for the circuit pattern formed on the opposite surface tothe laminating surface is not required. In accordance with the presentinvention, double side wiring in which one side is provided with aparticularly fine pattern is easily provided. Advantages of double sidewiring are in that options in wiring design are enhanced by crossinglines and via holes, that it is possible to reduce noise of high-speedICs by transmitting the ground potential to the vicinity of thenecessary location by wide lines, similarly, that it is possible toprevent the power potential from decreasing even in high-speed switchingby transmitting the power source potential to the vicinity of thenecessary location by wide lines, thus stabilizing the IC operation, andthat external noise can be blocked by electromagnetic interferencesealing. In this way, the importance of double side wiring increases asthe speed of ICs is increased and the number of electrode pads in an ICis increased.

In the example described above, after a surface of the flexible film,which is not laminated to the glass substrate, is provided with acircuit pattern, the flexible film is laminated to the glass substrate,and another circuit pattern is formed on the other surface of theflexible film. When both surfaces of the flexible film are provided withvery fine circuit patterns, the flexible film is preferably laminated toa glass substrate before the circuit pattern is formed on the firstsurface. In such a case, first, the surface processed later is laminatedto a glass substrate, and a circuit pattern is formed by a subtractiveprocess, semi-additive process, or full additive process. The surfaceprovided with the circuit is then laminated to another glass substrate,and the first glass substrate is peeled off. A circuit pattern is thenformed on the other surface by subtractive process, semi-additiveprocess, or full additive process. The glass substrate is then peeledoff.

In the process in which one of the glass substrates laminated to bothsurfaces of the flexible film is peeled, preferably, the self-stick,removable organic layer is a type in which adhesion is decreased byultraviolet irradiation, and the flexible film blocks ultraviolet lightor a metal layer is formed over the entire surface of the flexible filmso that the metal layer blocks the ultraviolet light. Additionally, asthe flexibility of the glass substrate is increased, the glass substrateis more easily peeled off. Therefore, the thickness of the glasssubstrate is preferably 0.7 mm or less, and more preferably 0.5 mm orless.

In the present invention, preferably, the laminated member for thecircuit board is formed, and after electronic components are mounted onthe laminated member for the circuit board, the flexible film isdetached from the reinforcing plate. When the electronic components,such as ICs, are bonded to the circuit board, in particular, when manyelectrode pads are bonded simultaneously, it is important to ensure lowdimensional change rate. Examples of the bonding methods include amethod in which a metal layer composed of tin, gold, solder, or the likeformed on the electrode pads of the circuit board is bonded to a metallayer composed of gold, solder, or the like formed on the electrode padsor bumps of the electronic components by thermal pressure bonding; and amethod in which, while pressure bonding a metal layer composed of tin,gold, solder, or the like formed on the electrode pads of the circuitboard and a metal layer composed of gold, solder, or the like formed onthe electrode pads or bumps of the electronic components to each other,an anisotropic conductive adhesive or nonconductive adhesive placedbetween the circuit board and the electronic components is hardened toperform mechanical bonding. In either method, the connecting sectionsare locally heated at 140 to 400° C. for 1 second to several minutes.The pressure applied to the connecting sections is large at 5 to 50 gper bump. If the self-stick, removable organic layer is deformed byhigh-temperature pressure, low dimensional change rate is not secured,and electrical connection reliability may be degraded due to thedeformation of the metal layer constituting the wiring circuit pattern.In wire bonding in which many electrode pads are connectedconsecutively, since high-temperature pressure is applied in order toperform metal bonding, the self-stick, removable organic layer may bedeformed as in the case of simultaneous bonding. In such bonding underhigh-temperature pressure, the deformation in the thickness direction ofthe circuit board is referred to as “sinking”, and the sinking ispreferably 6 μm or less, and more preferably 3 μm or less, so thatelectrical connection reliability is ensured.

The self-stick, removable organic layer of the present invention is softin order to provide tackiness. Although the self-stick, removableorganic layer with a thickness of 10 to 20 μm is usually used, in thepresent invention, by extremely decreasing the thickness of theself-stick, removable organic layer, the circuit board can be preventedfrom being deformed during electronic component bonding underhigh-temperature pressure. Preferably, the high-temperature pressurehead used for bonding electronic components also acts as a part forsupporting the electronic components in order to facilitate heating ofthe connecting sections. In such a case, heating and pressing areperformed from the flexible film side provided with the circuit pattern.Therefore, as the thickness of the flexible film and the thickness ofthe circuit pattern under the high-temperature pressure head areincreased, the influence of the high-temperature pressure on theself-stick, removable organic layer is decreased, and the thickness ofthe self-stick, removable organic layer can be increased. Preferably,the thickness of the organic layer is 5 μm or less. On the other hand,adhesion of the self-stick, removable organic layer increases as thethickness of the self-stick, removable organic layer increases, and thedetachment of the flexible film in the fabrication process is easilyprevented. In addition, roughness of the flexible film surface and thedifference in level of circuit pattern formed thereon are easily buriedto provide flat surfaces. Therefore, the thickness of the self-stick,removable organic layer is preferably in the range of 0.05 to 5 μm, morepreferably in the range of 0.1 to 3 μm, and most preferably in the rangeof 0.2 to 2 μm.

In the method for laminating the flexible film to the reinforcing plateof the present invention, in order not to distort the flexible film sothat low dimensional change rate is maintained, preferably, applicationof a force in the in-plane direction of the flexible film should beavoided as much as possible. In particular, when a circuit pattern isformed on one surface of the flexible film before the flexible film islaminated to the reinforcing plate, lamination is desirably performedwith low stress in order to ensure alignment accuracy.

A method and apparatus for laminating the flexible film of the presentinvention will be described with reference to the drawings.

FIG. 1 is a front sectional view which schematically shows a centralpart of a laminator 1 (in which cross sections are shown by overallfilling and oblique lines), and FIG. 2 is a sectional view taken alongthe line X-X of FIG. 1.

A laminator 1 includes a stage 3 for holding a substrate 6 which is areinforcing plate, a film holding sheet 2 for holding a film 4 placedright above the substrate 6, a squeegee 8 for simultaneously pressingthe film holding sheet 2 and the film 4 to the substrate 6 by applyingpressure, and an electrostatic charging device 12 for impartingelectrostatic force to the film 4 to adsorb the film holding sheet 2.Herein, the film 4 is thin and flexible. Furthermore, suction holes arearranged on the upper surface of the stage 3 and the substrate 6 can beheld by suction by the operation of a source of vacuum, not shown in thedrawing. By the guidance of a pair of rails 25 placed on a base 9 and apair of guides 24 engaged with the rails 25, the stage 3 is mounted onthe guides 24. The stage 3 is horizontally movable in FIG. 1. A nut 26is attached to the bottom of the stage 3. The nut 26 is engaged with aball screw 20 which is rotatably held by brackets 22 and 16, and theball screw 20 is directly coupled to a motor 18 which is mounted on aside face of the base 9 with the bracket 16 therebetween. Consequently,the stage 3 can be reciprocated at a predetermined speed by the rotationof the motor 18.

The film holding sheet 2 is composed of a flexible cloth or thin filmfixed on a frame 10, and is supported by supports 44 a and 44 b whichextend in the traveling direction of the stage 3 at both sides in thewidth direction (in a direction orthogonal to the traveling direction)of the stage 3. Since the supports 44 a and 44 b are coupled to a pairof vertically movable linear cylinders 46, the film holding sheet 2 canbe vertically reciprocated by the operation of the linear cylinders 46.Consequently, the film 4 held by the film holding sheet 2 faces thesubstrate 6 substantially in parallel and the distance therebetween canbe set arbitrarily. The distance can be set by monitoring the positionsby linear scales built in the linear cylinders 46.

A pair of rails 38 extending in the traveling direction of the stage 3are mounted on the supports 44 a and 44 b which support the film holdingsheet 2 so as to sandwich the stage 3. Guides 36 a and 36 b are placedon the pair of rails 38 so as to be movable in the longitudinaldirection of the rails 38. Bearings 32 a and 32 b are mounted on theguides 36 a and 36 b, respectively, and a squeegee support 28 isrotatably fitted to the bearings 32 a and 32 b. Consequently, thesqueegee 8 fastened to the squeegee support 28 is also rotatable. Amoving body 40 constituting one part of the linear motor 43 is fixed tothe guide 36 a and a stator 42 constituting the other part of the linearmotor 43 is fixed to the support 44 a. Consequently, the squeegeesupport 28 and the squeegee 8 can be reciprocated in the travelingdirection of the stage 3 by the operation of the linear motor 43 and theguidance of the rails 38 and the guides 36 a and 36 b. Furthermore, thesqueegee support 28 rotatably supported by the bearings 32 a and 32 b isdirectly coupled to a rotary cylinder 34. Consequently, the squeegee 8fastened to the squeegee support 28 can be pressed against the filmholding sheet 2 or the press can be released by the rotation in thedirections indicated by the arrows. The contact section of the squeegee8 to the film holding sheet 2 is preferably edge-shaped. Additionally,since the squeegee 8 is eventually supported by the supports 44 a and 44b, the squeegee 8 can be vertically moved together with the film holdingsheet 2 by the vertical operation of the linear cylinders 46.

The electrostatic charging device 12 extends in the width direction ofthe stage 3 in a range larger than the width of the stage, and issupported by a column 14 above the base 9. The electrostatic chargingdevice 12 blows positively or negatively charged ionic air to the objectlying beneath the device over the width of the stage 3, and by passingthe film 4 attracted to the top of the stage 3 beneath the electrostaticcharging device 12, it is possible to impart electrostatic force to thefilm 4. Similarly, by passing the electrostatic charging device 12 abovethe film holding sheet 2, it is also possible to impart electrostaticforce to the film holding sheet 2. Additionally, an organic layer 7having tackiness is preliminarily attached to the upper surface of thesubstrate 6.

Next, a lamination method using the laminator 1 will be described withreference to FIGS. 3(a) to 3(f). FIGS. 3(a) to 3(f) are front viewswhich schematically show steps in a lamination method in accordance withthe present invention.

First, the stage 3 is moved to and stopped at the left edge positionshown by the broken lines in FIG. 1, and the film 4 is placed on thestage 3 by a transport device (not shown in the drawing) and fixed byvacuum suction (FIG. 3(a)). While the stage 4 is moved rightward at aconstant speed, the film 4 is passed below the electrostatic chargingdevice 12 which emits positively charged ionic air downward so that thefilm 4 is positively charged. When the stage 3 reaches the positionbeneath the film holding sheet 2, the stage 3 is stopped and the suctionof the film 4 is released. The linear cylinders 46 are moved downward tobring the film holding sheet 2 in close proximity to the film 4 on thestage 3, and are stopped when a predetermined distance is attained (FIG.3(b)). The distance between the film 4 and the film holding sheet 2 ispreferably 10 mm or less, or the face of the film 4 and the face of thefilm holding sheet 2 may be brought into contact with each other. Next,by rotating the rotary actuator 34, the squeegee 8 is pressed againstthe upper surface of the film holding sheet 2 (the opposite surface tothe surface holding the film 4) so that the film 4 is sandwiched betweenthe film holding sheet 2 and the upper surface of the stage 3. Thelinear motor 43 is then driven to transport the squeegee 8 from the leftedge to the right edge of the film 4, and the flexible film 4 on thestage 3 is transferred to the film holding sheet 2 by electrostaticforce (FIG. 3(c)).

When the film 4 is held on the film holding sheet 2, the squeegee 8 isdetached from the film holding sheet 2 by rotating the rotary cylinder34 in the opposite direction, and the linear cylinders 46 are movedupward to transport the film holding sheet 2 upward and left to standfor a while. At this stage, the squeegee 8 is moved to the left edge byoperating the linear motor 43 and the stage 3 is moved to and stopped atthe left edge position again by driving the motor 18. The substrate 6provided with the organic layer 7 having tackiness on the top is placedon the stage 3 by a transport device (not shown in the drawing), andfixed by suction (FIG. 3(d)). After fixing by suction, the stage 3 ismoved rightward and stopped when the stage 3 reaches the positionbeneath the flexible film 4 held by the film holding sheet 2 (FIG.3(e)). The stop position of the stage 3 is set so that the film 4 can belaminated to the predetermined position on the substrate 6.

The linear cylinders 46 are driven to bring the film holding sheet 2 inclose proximity to the substrate 6 on the stage 3, and stopped when apredetermined distance is attained between the film 4 and the substrate6. The distance between the film 4 and the substrate 6 is preferably 10mm or less. By operating the rotary cylinder 34, the squeegee 8 ispressed against the top of the film holding sheet 2 by the rotation, andthe film 4 held by the film holding sheet 2 is pressed to the substrate6. By driving the linear motor 43, the squeegee 8 is moved from the leftedge to the right edge of the film 4, and the film 4 held by the filmholding sheet 2 is thereby transferred to the substrate 6 on the stage 3(FIG. 3(f)). By this operation, the flexible film 4 is laminated to thesubstrate 6, and strongly laminated by the adhesion of the organic layer7. When the squeegee 8 reaches the right edge and stops, the rotarycylinder 34 is rotated in the opposite direction to move the squeegee 8away from the film holding sheet 2. The linear cylinders 46 are thenmoved upward to elevate the film holding sheet 2 and suction of thestage 3 is released. The substrate 6, to which the film 4 is laminated,is carried to the next fabrication step by a transport device (not shownin the drawing). By repeating the same operation, another film 4 andanother substrate 6 are laminated.

In accordance with the lamination method of the present invention,lamination is enabled with a very small dimensional change rate of thefilm at 0.01% or less. The reason for this is that, when the flexiblefilm on the stage 3 is held by the film holding sheet 2, the flexiblefilm 4 can be transferred as it is with substantially no change in thesize. This is because 1) since the film holding sheet 2 which iselastically deformable in plane is used, the film holding sheet followsthe roughness of the stage 3 and the film 4, and thereby the plane ofthe film 4 can be uniformly held; 2) since the distance between the filmholding sheet 2 and the film 4 is small at 10 mm or less when theirfaces are brought in close proximity, the angle θ (refer to FIG. 3(c))between the film holding sheet and the stage 3 is small at 5° or lesswhen the squeegee 8 is moved under pressure; thereby, in the mannersimilar to that in the case when the film holding sheet 2 is brought inclose contact with the film 4 substantially in parallel and then thefilm 4 is transferred to the film holding sheet 2, it is possible totransfer the film 4 from the stage 3 to the film holding sheet 2 withoutchanging the relative position between the film 4 on the stage 3 and thefilm 4 on the film holding sheet 2, and therefore, strain is not causedin the film 4, resulting in no dimensional change; and 3) since thecontact section of the squeegee 8 to the film holding sheet is a line,the film holding sheet 2 and the film 4 are not deformed due topressure, and air capturing can be prevented efficiently duringlamination.

When the film 4 which is held by the film holding sheet 2 without changein the size is transferred (laminated) to the substrate 6 provided withthe organic layer 7, similarly, the film 4 can be transferred to thesubstrate 6 as it is, i.e., in the state that the film 4 is being heldby the film holding sheet 2. The reasons for this are, similarly, 1)since the film holding sheet which is elastically deformable in plane isused, the film holding sheet 2 follows the roughness of the surface ofthe substrate 6, and thereby the film 4 can be brought into contact withthe substrate 6 uniformly; 2) since the distance between the filmholding sheet 2 and the substrate 6 is small at 10 mm or less, the angleθ (refer to FIG. 3(f)) between the film holding sheet and the substrate6 is small at 5° or less when pressed by the squeegee; thereby, becausethe film 4 is brought into close contact with the substrate 6substantially in parallel and then is transferred to substrate 6, it ispossible to transfer the film 4 from the film holding sheet 2 to thesubstrate 6 without changing the relative position between the film 4 onthe film holding sheet 2 and the film 4 on the substrate 6, andtherefore, strain is not caused in the film 4, resulting in no change inthe size; and 3) since the contact section of the squeegee 8 to the filmholding sheet is a line, the film 4 is not deformed due to pressure andair capturing can be prevented efficiently during lamination.

Additionally, in order to control the dimensional change rate at 0.005%or less, the distance between the film 4 and the substrate 6 which aresubstantially in parallel is set at preferably 5 mm or less, and morepreferably 1 mm or less.

With respect to the squeegee 8, in order to enable the contact line tobe thinner, the tip which acts as the contact part is preferablyedge-shaped, or rounded with an r value of 5 mm or less. The materialfor the tip may be a hard material, such as a metal, ceramic, orsynthetic resin. Alternatively, in order to apply pressure uniformly, arubber with a Shore hardness of 50 to 90 may be used. Preferably, thesqueegee 8 and the film holding sheet 2 are coated with a fluorocarbonresin or the like so that satisfactory sliding is enabled and dustgeneration is suppressed when the squeegee 8 is pressed against andmoved over the film holding sheet 2. In order to further suppress dustgeneration, the squeegee 8 may be a rotatable pressure roll. As thepressure roll, either a metal roll or a rubber-coated roll may be used.In order to make the contact line thinner to avoid capturing of air,preferably a roll with a small diameter of 30 mm or less is employed.The pressure by the squeegee is preferably 5 to 500 N/m, and morepreferably 10 to 100 N/m. The moving rate of the squeegee duringlamination is preferably 0.1 to 50 m/min, and more preferably 5 to 15m/min.

The film holding sheet 2 is preferably composed of a flexible cloth orthin film because it must be elastically deformable in plane. The frame10 which supports the film holding sheet desirably has satisfactorystrength and flatness, and is preferably composed of a metal, syntheticresin, fiber reinforced resin, or the like.

As the flexible cloth, a mesh cloth obtained by weaving polyester,polypropylene, liquid crystal polymer or stainless steel fibers ispreferably used. It is acceptable to form openings in the cloth using aphotosensitive coating film or the like. Examples of the thin films usedin the present invention include plastic films, such as polyester,polyimide, and polyphenylene sulfide films. It is acceptable to formopenings by cutting such plastic films. Furthermore, a hard rubber mayalso be employed.

As the means for holding the film 4 on the film holding sheet 2, inaddition to the electrostatic force described above, surface tension ofa liquid, adhesion of an organic substance, or vacuum suction may beused. Surface tension of a liquid, electrostatic force, or adhesion ofan organic substance is preferably used because the holding power andthe peel strength are easily balanced with each other and a large-scaleapparatus is not required. The methods in which surface tension is usedand in which electrostatic force is used are more preferable compared tothe method in which adhesion of an organic substance is used because ofsuperior durability and reproducibility.

The method in which electrostatic force is used is not particularlylimited as long as one of the film holding sheet 2 and the film 4 ischarged or polarities of the charges of the film holding sheet 2 and thefilm 4 are opposite to each other. Specifically, in order to chargeeither the film holding sheet 2 or the film 4, in addition to the methodof applying positive or negative ionic air as described above, when thefilm holding sheet 2 is electrically conductive, by applying a highvoltage, the film 4 can be attracted thereto. Furthermore, when a metalfilm is formed on the surface of the film 4, by applying a high voltageto the metal film, the film holding sheet 2 and the film 4 are attractedto each other, and thereby holding is performed.

As an example of the method in which surface tension of a liquid isused, before holding, a liquid is attached to the surface of the film 4or the film holding sheet 2 by coating, spraying, or dew condensation,and the film 4 and the film holding sheet 2 are put on each other toform a thin layer of the liquid between the film 4 and the film holdingsheet 2. In another effective method, a liquid is scattered on thecontact surface of the film holding sheet 2 and/or the film 4beforehand, both are put on each other, and the surface opposite to thecontact surface is squeezed by moving a squeegee so that the thicknessof the liquid layer between the film holding sheet 2 and the film 4 isdecreased. In another method, the film holding sheet 2 composed of aflexible cloth with openings and the film 4 are brought into contactwith each other in the dry state, a liquid is scattered to the filmholding sheet 2 side opposite to the contact section, and the liquid issupplied to the space between the film holding sheet 2 and the film 4through the openings of the film holding sheet by a squeegee. Thismethod is preferred because liquid supply and squeegeeing aresimultaneously performed, resulting in a reduction in takt time. As theliquid for imparting adhesion, water is preferably used because it hasrelatively large surface tension and is unlikely to act as an impurityin the subsequent fabrication steps. In order to adjust surface tension,an alcohol may be added to water.

As an example of the method in which adhesion of an organic substance isused, an adhesion layer is provided between the laminating surfaces ofthe film holding sheet 2 and the film 4. In such a case, an adhesivewith weak to strong adhesion is preferably formed in a dot shape orstripe shape to decrease adhesion so that the film 4 is easily detachedfrom the film holding sheet 2. Consequently, adhesion and peel strengthare easily balanced, and durability is improved. Preferably, dots with adiameter of 0.1 to 2 mm are arrayed with a separation of 1 to 10 mmbecause adhesion and peel strength are balanced and satisfactory holdingpower of the flexible film is ensured.

A method for making a circuit board of the present invention will bedescribed. However, the present invention is not limited thereto.

To an aluminoborosilicate glass with a thickness of 0.7 mm, a silanecoupling agent, as an auxiliary adhesive layer, is applied by a spincoater, blade coater, roll coater, bar coater, or die coater, by screenprinting, or the like. A spin coater is preferably used in order toapply a thin film of a silane coupling agent with relatively lowviscosity uniformly to individual sheet substrates periodicallydelivered. After the silane coupling agent is applied, drying isperformed by heating or by vacuum, and a silane coupling auxiliaryadhesive layer with a thickness of 20 nm is obtained.

An ultraviolet curable, self-stick, removable adhesive agent is appliedto the silane coupling agent layer by a spin coater, blade coater, rollcoater, bar coater, or die coater, by screen printing, or the like. Inorder to apply the ultraviolet curable, self-stick, removable adhesiveagent with relatively high viscosity uniformly to the individual sheetsubstrates periodically delivered, a die coater is preferably used.After the self-stick, removable adhesive agent is applied, drying isperformed by heating or by vacuum to obtain a self-stick, removableadhesive layer with a thickness of 1 μm. An air-shielding film composedof a release film in which a silicone resin layer is placed on apolyester film is attached to the adhesive layer of rework style and isleft to stand for one week at room temperature. This period is referredto as “maturation”, in which crosslinking of the self-stick, removableadhesive agent proceeds and adhesion gradually decreases. The storagetime and temperature are selected so as to obtain desired adhesion.Instead of attaching the air-shielding film, storing may be performed ina nitrogen atmosphere or in a vacuum. A self-stick, removable adhesiveagent may be applied to a long web, dried, and then transferred to areinforcing plate.

Next, a polyimide film with a thickness of 25 μm is prepared. Theair-shielding film on the glass substrate is removed and the polyimidefilm is attached to the glass substrate. As described above, at leastone surface of the polyimide film may be provided with a metal layer.The polyimide film which has been cut into cut sheets with apredetermined size may be used, or the polyimide film may be laminatedand cut sequentially while unwinding a roll of the polyimide film. Insuch a lamination process, the method in which the flexible film is heldon the film holding sheet and pressed against the reinforcing plate totransfer the flexible film to the reinforcing plate, as described above,is preferably used.

A circuit pattern is then formed on the opposite surface to thelaminated surface of the polyimide film by a full additive process, asemi-additive process, or a subtractive process. The semi-additiveprocess is preferably employed because fine pitch patterns can be formedwith high productivity.

In the semi-additive process, an underlayer for ensuring electricalconductivity is formed by sputtering chromium, nickel, copper, or analloy of these metals. Before the underlayer is formed, in order toimprove adhesion between the underlayer and the polyimide film, thesurface of the polyimide film may be subjected to plasma treatment,reverse sputtering, primer layer application, or adhesive layerapplication as appropriate. Above all, application of an adhesive layercomposed of an epoxy resin, acrylic resin, polyamide resin, polyimideresin, NBR, or the like is preferred because of its large adhesionimproving effect. The adhesive preferably has high hardness in order toprevent sinking due to high temperature and high pressure in theelectronic-component-connecting step, and preferably has a thickness of2 μm or less. Such treatment and application may be performed before orafter the lamination of the reinforcing plate. Preferably, a treatmentwith a roll-to-roll system is performed on a long polyimide film beforethe reinforcing plate is laminated in view of improvement inproductivity.

The thickness of the underlayer is in the range of 1 to 1,000 nm. It iseffective in securing sufficient conductivity for subsequentelectroplating, in improving the adhesion of the metal layer, and inpreventing pinhole defects to deposit a copper layer by sputteringfurther on the underlayer at a thickness of 50 to 3,000 nm. Theunderlayer may be formed after the flexible film is laminated to thereinforcing plate, or may be formed, for example, on a long web beforelamination. A photoresist is applied to the underlayer thus formed by aspin coater, blade coater, roll coater, or die coater, or by screenprinting, followed by drying. The photoresist is exposed through aphotomask with a predetermined pattern to form a resist layer in thesections in which the plating film is not required. The exposedphotoresist is developed. Electroplating is then performed using theunderlayer as an electrode. As the electroplating solution, a coppersulfate plating solution, copper cyanide plating solution, copperpyrophosphate plating solution, or the like is used. A copper-platinglayer is formed at a thickness of 2 to 20 μm, and the photoresist isremoved. The underlayer is removed by slight etching to obtain a circuitpattern. Furthermore, plating of gold, nickel, tin, or the like isperformed as required.

In the circuit-pattern formation step, connecting holes may be formed inthe polyimide film. That is, via-holes may be formed in order to provideelectrical connection with the metal layer formed on the surfacelaminated to the reinforcing plate, or holes for placing balls for aball grid array package may be formed. In order to produce a fine pitchpattern, since dimensional change rate of the connecting holes isimportant as well as dimensional change rate of the circuit pattern,preferably, after the flexible film is laminated to the reinforcingplate to secure dimensional stability, the connecting holes are formedfrom the opposite surface to the laminated surface of the polyimidefilm. In order to form the connecting holes, laser drilling by a carbondioxide laser, YAG laser, excimer laser, or the like, or chemicaletching may be employed. When laser drilling is employed, a metal layeris preferably formed as a stopper layer on the surface of the polyimidefilm to which the reinforcing plate is laminated. As a chemical etchant,hydrazine, potassium hydroxide, or the like may be used. As a mask forchemical etching, a patterned photoresist or metal layer may be used.When electrical connection is made, after connecting holes are formed,preferably, the inner surfaces of the holes are plated simultaneouslywith the formation of the metal layer pattern on the polyimide filmdescribed above. The connecting hole for electrical connection has adiameter of 15 to 200 μm. The hole for placing the ball preferably has adiameter of 50 to 800 μm, and more preferably 80 to 800 μm.

Next, electronic components, such as IC chips, resistors, andcapacitors, are mounted on the circuit pattern thus formed. Anyapparatus for mounting electronic components may be used in the presentinvention as long as it has a function of optical position detection andan alignment mechanism, such as a movable stage, so that low dimensionalchange rate is ensured. The present invention is particularly effectivein securing mounting accuracy of large-scale ICs with small connectionpitch and a large number of pins. The IC package form is notparticularly limited, and the present invention is applicable to all ofbare chips, lead frame types, and ball grid array types. Preferably, thepresent invention is applied to bare chips or ball grid array types inwhich the number of pins is increased.

The method for connecting electronic components to the circuit board inthe present invention is not particularly limited. In the method inwhich many electrode pads or bumps are connected simultaneously, it isimportant to ensure low dimensional change rate, to which the presentinvention is preferably applied. Examples of the methods for connectingmany electrode pads simultaneously include a method in which a metallayer composed of tin, gold, solder, or the like formed on the electrodepads of the circuit board is bonded to a metal layer composed of gold,solder, or the like formed on the electrode pads or bumps of theelectronic components by thermal pressure bonding; a method in which,while pressure bonding a metal layer composed of tin, gold, solder, orthe like formed on the electrode pads of the circuit board and a metallayer composed of gold, solder, or the like formed on the electrode padsor bumps of the electronic components to each other, an anisotropicconductive adhesive or nonconductive adhesive placed between the circuitboard and the electronic components is hardened to perform mechanicalbonding; and a method in which electronic components are temporarilyfixed on a solder paste pattern-printed on electrode pads, and thenconnection is performed by simultaneous reflowing. The present inventionis greatly effective in the connecting method by thermal pressurebonding.

By mounting electronic components in the state in which the circuitboard is laminated to the glass substrate, it is possible to eliminatecontrolling of temperature and humidity and moisture proof packagingafter the fabrication of the circuit board until mounting of electronicdevices. In particular, in flexible films, an irreversible dimensionalchange is often caused by moisture absorption, and the present inventiongreatly contributes to ensuring of the connecting accuracy between thecircuit board and electronic devices. Furthermore, even if the circuitboard is deformed by stress caused when the circuit board is peeled offthe glass substrate, by mounting electronic devices to the circuit boardbefore the circuit board is peeled off the glass substrate, it ispossible to prevent impairment of the connecting accuracy when theelectronic devices are connected.

After the circuit board and the electronic components are connected toeach other, the circuit board is peeled off the glass substrate. Beforepeeling, preferably, the polyimide film provided with the circuitpattern is separated into single pieces or sets of single pieces by alaser, a jet of high-pressure water, a cutter, or the like becausehandling after peeling is facilitated. In addition, if the polyimidefilm is cut into single pieces or sets of single pieces when the circuitpattern is formed, stress is unlikely to remain in the polyimide film,which is desirable.

The present invention will be described in more detail based on theexamples below. However, the present invention is not limited thereto.The performance values were measured according to the following methods.

-   Young's modulus of glass plate: Calculated according to JIS R1602-   Young's modulus of metal plate: Calculated according to ASTM    E1876-01-   Peel strength: A polyimide film was laminated to a self-stick,    removable adhesive layer formed on a reinforcing plate, and then the    polyimide film was cut into a width of 10 mm. The strength by which    the 10 mm wide polyimide film was peeled in the straight angle    direction at a peel rate of 300 mm/min using “Tensilon” manufactured    by TMI was defined as the peel strength.

EXAMPLE 1

As an auxiliary adhesive, γ-aminopropyltriethoxy silane was dissolved inisopropyl alcohol so as to obtain a concentration of 5% by weight. Theauxiliary adhesive solution was applied by a spin coater to a squarealuminoborosilicate glass with a side of 300 mm and a thickness of 0.7mm, followed by drying at 100° C. for 5 minutes. The dried auxiliaryadhesive layer had a thickness of 300 nm.

A mixture obtained by mixing an acrylic adhesive “SK-DYNE” SW-11A(manufactured by Soken Chemical and Engineering Co., Ltd.), in whichadhesion was decreased by ultraviolet curing, with a curing agent L45(manufactured by Soken Chemical and Engineering Co., Ltd.) at a mixingratio of 50:1 was applied to the glass substrate provided with theauxiliary adhesive layer, followed by drying at 80° C. for 2 minutes.The dried self-stick, removable adhesive layer had a thickness of 1 μm.Next, an air-shielding film composed of a film in which an easilyreleasable silicone resin layer was placed on a polyester film wasattached to the adhesive layer and was left to stand for one week. Theglass substrate had a Young's modulus of 7,140 kg/mm², and the productof the Young's modulus (kg/mm²) and the cube of the thickness (mm) was2,449 kg·mm.

An adhesive for improving the adhesion of the metal layer was preparedas described below. Into a flask in which the atmosphere was replacedwith nitrogen, 228 parts by weight of N,N-dimethylacetamide was put and19.88 parts by weight of1,1,3,3-tetramethyl-1,3-bis(3-aminopropyl)disiloxane was dissolvedtherein. 25.76 parts by weight of 3,3′,4,4′-benzophenonetetracarboxylicdianhydride was added thereto and stirred in the nitrogen atmosphere at10° C. for 1 hour. Reaction was carried out while stirring at 50° C. for3 hours, and an adhesive composed of polyimide precursor varnish wasthereby obtained.

Using a comma coater, the adhesive was continuously applied to onesurface of a long polyimide film (“UPILEX” manufactured by UbeIndustries, Ltd.) with a Young's modulus of 930 kg/mm², a thickness of25 μm, and a width of 300 mm. Next, drying was performed at 80° C. for10 minutes, at 130° C. for 10 minutes, and at 150° C. for 15 minutes,and curing was performed at 250° C. for 5 minutes. The thickness of thecured adhesive layer was 0.5 μm.

The polyimide film on which the adhesive was deposited was cut into asquare with a side of 300 mm and was stored in an atmosphere of 25° C.and 45% RH for 10 hours. The polyimide film was then placed on the stage3 provided with a vacuum suction mechanism shown in FIGS. 1 and 3 withthe adhesive layer surface facing upward, and vacuum suction wasperformed. Next, the polyimide film was passed below the electrostaticcharging device 12 while moving the stage 3. At this time, negativeionic air was blown from the electrostatic charging device 12 tonegatively charge the polyimide film. A 100-mesh screen gauze composedof polyester filaments was moved downward and brought into contact withpolyimide film 4. In such a state, the stage was moved so that thescreen gauze 2 passed below the electrostatic charging device 12 whichwas switched so as to blow positive ionic air, and the screen gauze 2was positively charged. The surface of the screen gauze 2 opposite tothe stage was squeegeed by a rubber plate 8 to ensure the adhesionbetween the polyimide film 4 and the screen gauze 2. The vacuum suctionof the stage 3 was stopped, the screen gauze 2 was moved upward, and thepolyimide film 4 was transferred to the screen gauze 2.

The glass substrate 6 provided with the adhesive layer 7 was placed onthe stage 3 provided with the vacuum suction mechanism. Theair-shielding film on the adhesive layer was removed in advance. Thescreen gauze 2 laminated with the polyimide film 4 was moved to aposition above the glass substrate 6.

The screen gauze 2 laminated with the polyimide film 4 was moveddownward and placed parallel to the glass substrate with a separation of0.7 mm. Next, the surface of the screen gauze 2 opposite to the surfaceabutting on the polyimide film was squeegeed by a rubber plate 8 with aShore hardness of 50 to press the polyimide film 4 against theself-stick, removable adhesive layer 7, and the polyimide film 4 wasthereby transferred to the glass substrate. The screen gauze was passedbelow the electrostatic charging device 12 which was switched so as toblow positive and negative ionic air, and the charges of the screengauze were neutralized.

The glass substrate laminated with the polyimide film was removed fromthe stage and was irradiated with ultraviolet light at 1,000 mJ/cm² fromthe glass substrate side to cure the self-stick, removable adhesivelayer.

On the polyimide film laminated on the glass substrate, achromium-nickel alloy layer with a thickness of 4 nm and a copper layerwith a thickness of 200 nm were deposited in that order by sputtering.In the alloy composition, the weight ratio of chromium to nickel was20:80.

A positive photoresist was applied to the copper layer by a spin coaterand dried at 110° C. for ten minutes. The photoresist was exposedthrough a photomask. Next, the photoresist was developed, and a resistlayer with a thickness of 10 μm was thereby formed in the sections whichdid not require a plating layer. In the photomask pattern for testing,one unit consisted of 380 connecting pads (20 μm wide, 200 μm long) witha pitch of 50 μm arrayed in two parallel columns and a distance of 1.5mm between the centers of the adjacent pads, and respective units wereuniformly arrayed with a pitch of 40 mm in 7 rows and 7 columns on asquare polyimide film with a side of 300 mm. At the same time, for thepurpose of measuring length, 4 markers were provided on the photomaskpattern at four points diagonally apart from the center of the substratewith a distance of approximately 141 mm (the distance between theindividual points being 200 mm in parallel to the side).

Next, using the copper layer as an electrode, a copper layer with athickness of 5 μm was formed by electroplating. A copper sulfate platingsolution was used as the electroplating solution. The photoresist wasremoved by a photoresist stripper, and the copper layer and thechromium-nickel alloy layer below the resist layer were removed by softetching using a hydrogen peroxide-sulfuric acid aqueous solution. Anickel layer with a thickness of 1 μm and a gold layer with a thicknessof 0.2 μm were deposited by electroplating in that order on thecopper-plating layer. The nickel electroplating was performed in a Wattbath. As the gold electroplating solution, a neutral gold platingsolution including aurous potassium cyanide was used. A metal layerpattern was thereby formed.

Using a 150-mesh polyester screen, a solder resist NPR-90 (manufacturedby Nippon Polytex) was applied by a screen printer to the entire surfaceof the polyimide film provided with a metal pattern, followed by dryingat 70° C. for 30 minutes. Next, in order to remove the solder resist onthe electrode pad units arrayed in 7 rows and 7 columns and on themarkers for measuring length, the solder resist was irradiated withultraviolet light at 600 mJ/cm² through a photomask, and the solderresist was developed while spraying 1% by weight sodium carbonateaqueous solution. Curing was performed at 150° C. for 30 minutes to curethe solder resist. A laminated member for a circuit board was therebyobtained.

The distance between the two points, which were provided for measuringlength as described above, originally about 283 mm apart diagonally (200mm in the x direction, 200 mm in the y direction) was measured by alength-measuring device SMIC-800 (manufactured by Sokkia Co., Ltd.). Asa result, dimensional change rate was extremely satisfactory, i.e.,within ±5 μm (±5 μm divided by 283 mm equals ±0.0018%) relative to thephotomask pattern.

Furthermore, the resultant laminated member for the circuit board wasleft to stand in an atmosphere of 30° C. and 80% RH for one week. Whileheating an IC chip model, in which 380 bumps plated with gold werearrayed with a pitch of 50 μm per one row and two rows were arrayed witha separation of 1.5 mm, at 150° C. from the chip side, using anultrasonic bonder FC2000 (manufactured by Toray Engineering Co., Ltd.),metal diffusion bonding with the electrode pads on the circuit board wasperformed. Each bump had a width of 30 μm, a length of 50 μm, and aheight of 14 μm. The pressure for each bump was 30 g. The alignment ofthe bumps of the IC chip model with the electrode pads on the circuitboard was satisfactory. A cross section of the connecting part was takenand observed by an electron microscope. As a result, the sinking of thebumps was small at 1.7 μm, which caused no problems in reliability.

An edge of the polyimide film was vacuum-sucked and the polyimide filmwas gradually peeled off the glass substrate. A circuit board wasthereby obtained. At this stage, the peel strength was 2 g/cm, and theproduct A×B×C, i.e., the product of the peel strength A (g/cm), thereciprocal B (1/μm) of the thickness of the polyimide film, and thereciprocal C (mm²/kg) of the Young's modulus of the polyimide film, was8.6×10⁻⁵. The polyimide film was not detached from the adhesion layer inthe circuit-pattern-forming step. When the polyimide film was peeledoff, the polyimide film was peeled off at the interface with theadhesion layer, and curling of the polyimide film did not occur. Theresultant circuit board was stored in an atmosphere of 25° C. and 45% RHfor 10 hours. The distance between the two points, which were providedfor measuring length as described above, originally about 283 mm apartdiagonally (200 mm in the x direction, 200 mm in the y direction) wasmeasured by the length-measuring device SMIC-800. As a result,dimensional change rate was maintained extremely satisfactorily, i.e.,within ±5 μm (±5 μm divided by 283 mm equals ±0.0018%) relative to thephotomask pattern.

EXAMPLE 2

An adhesive for improving the adhesion of a metal layer was prepared inthe same manner as that in Example 1. The adhesive was continuouslyapplied to a long polyimide film (“UPILEX” manufactured by UbeIndustries, Ltd.) with a thickness of 25 μm and a width of 300 mm,followed by drying and curing in the same manner as that in Example 1.The other surface of the polyimide film was coated with the adhesivesimilarly, followed by drying and curing.

On one of the surfaces of the polyimide film provided with the adhesivelayers, a chromium-nickel alloy layer with a thickness of 5 nm and acopper layer with a thickness of 200 nm were deposited in that order bya sputtering apparatus with a roll-to-roll system. In the alloycomposition, the weight ratio of chromium to nickel was 20:80. Acopper-plating layer with a thickness of 5 μm was formed on the copperlayer by an electroplating apparatus with a roll-to-roll system. As theplating solution, copper sulfate was used.

The polyimide film provided with the copper-plating layer was cut into asquare sheet with a side of 300 mm. A dry film was laminated on thecopper-plating layer by a roll laminator, and a dry film resist patternwas formed by exposing the dry film resist through a photomask and bydeveloping. In the photomask pattern for testing, one unit consisted of28 pads with a diameter of 500 μm arrayed on a straight line with apitch of 10 mm, and respective units were arrayed with a pitch of 40 mmin 6 rows in parallel from a position 50 mm apart from the side of thesquare polyimide film with a side of 300 mm. Furthermore, every otheradjacent pad was connected with a line with a width of 100 μm.

By showering a ferric chloride aqueous solution onto the polyimide filmprovided with the dry film resist pattern, the copper layer waspatterned, and also the chromium-nickel alloy layer under the copperlayer was patterned. A wiring pattern and alignment marks were therebyformed. The dry film resist was then removed by a resist stripper. Apolyimide film provided with the pads and the wiring pattern on onesurface thereof was thereby obtained.

In the same manner as that in Example 1, an auxiliary adhesive layer andan adhesive layer were formed on a square aluminoborosilicate glass witha side of 300 mm and a thickness of 0.7 mm. An air-shielding film wasattached thereto and left to stand for one week.

The polyimide film provided with the pads and the wiring pattern on onesurface thereof was stored in an atmosphere of 25° C. and 45% RH for 10hours. The polyimide film was then placed on the stage 3 provided with avacuum suction mechanism shown in FIGS. 1 and 3 with the surfaceprovided with the pads and the wiring pattern facing downward, andvacuum suction was performed. The polyimide film was laminated to theglass substrate in the same manner as that in Example 1.

The glass substrate laminated with the polyimide film was removed fromthe stage and was irradiated with ultraviolet light at 1,000 mJ/cm² fromthe glass substrate side to cure the adhesive layer.

Next, the polyimide film was shot with a short-pulse carbon dioxidelaser, a via hole with a top diameter of 120 μm and a bottom diameter of60 μm was formed at the position corresponding to the pad previouslyformed with a diameter of 500 μm. Smears on the bottom of the via holewere removed by immersing the polyimide film in a permanganic acidaqueous solution.

A chromium-nickel alloy layer and a copper layer were deposited on thepolyimide film in that order in the same manner as that in Example 1.Then a positive photoresist layer was formed on the copper layer,followed by exposure and development. In the photomask pattern fortesting, in the same manner as that in Example 1, one unit consisted of380 connecting pads (20 μm wide, 200 μm long) with a pitch of 50 μmarrayed in two parallel columns and a distance of 1.5 mm between thecenters of the adjacent pads, and respective units were uniformlyarrayed with a pitch of 40 mm in 7 rows and 7 columns on a squarepolyimide film with a side of 300 mm. At the same time, for the purposeof measuring length, 4 markers were provided on the photomask pattern atfour points diagonally apart from the center of the substrate with adistance of approximately 141 mm (the distance between the individualpoints being 200 mm in parallel to the side).

Next, using the copper layer as an electrode, a copper layer with athickness of 5 μm was formed by electroplating. A copper sulfate platingsolution was used as the electroplating solution. The photoresist wasremoved by a photoresist stripper, and the copper layer and thechromium-nickel alloy layer below the resist layer were removed by softetching using a hydrogen peroxide-sulfuric acid aqueous solution. Anickel layer with a thickness of 1 μm and a gold layer with a thicknessof 0.2 μm were deposited by electroplating in that order on the copperplating layer. As the nickel electroplating solution, a nickel sulfateplating solution was used. As the gold electroplating solution, anaurous potassium cyanide plating solution was used. A metal layerpattern was thereby formed. Next, in the same manner as that in Example1, a solder resist pattern was formed and a laminated member for acircuit board was obtained.

The distance between the two points, which were provided for measuringlength as described above, originally about 283 mm apart diagonally (200mm in the x direction, 200 mm in the y direction) was measured by alength-measuring device SMIC-800 (manufactured by Sokkia Co., Ltd.). Asa result, dimensional change rate was extremely satisfactory, i.e.,within ±5 μm (±5 μm divided by 283 mm equals ±0.0018%) relative to thephotomask pattern.

Furthermore, the resultant laminated member for the circuit board wasleft to stand in an atmosphere of 30° C. and 80% RH for one week. Whileheating an IC chip model, in which 380 bumps plated with gold werearrayed with a pitch of 50 μm per one row and two rows were arrayed witha separation of 1.5 mm, at 150° C. from the chip side, using anultrasonic bonder FC2000 (manufactured by Toray Engineering Co., Ltd.),metal diffusion bonding with the electrode pads on the circuit board wasperformed. Each bump had a width of 30 μm, a length of 50 μm, and aheight of 14 μm. The pressure for each bump was 30 g. The alignment ofthe bumps of the IC chip model with the electrode pads on the circuitboard was satisfactory. A cross section of the connecting part was takenand observed by an electron microscope. As a result, the sinking of thebumps was small at 1.7 μm, which caused no problems in reliability.

An edge of the polyimide film was vacuum-sucked and the polyimide filmwas gradually peeled off the glass substrate. At this stage, the peelstrength was 2 g/cm, and the product A×B×C, i.e., the product of thepeel strength A (g/cm), the reciprocal B (1/μm) of the thickness of thepolyimide film, and the reciprocal C (mm²/kg) of the Young's modulus ofthe polyimide film, was 8.6×10⁻⁵. The polyimide film was not detachedfrom the adhesion layer in the circuit-pattern-forming step. When thepolyimide film was peeled off, the polyimide film was peeled off at theinterface with the adhesion layer, and curling of the polyimide film didnot occur. The resultant circuit board was stored in an atmosphere of25° C. and 45% RH for 10 hours. The distance between the two points,which were provided for measuring length, originally about 283 mm apartdiagonally (200 mm in the x direction, 200 mm in the y direction) wasmeasured by the length-measuring device SMIC-800. As a result,dimensional change rate was maintained extremely satisfactorily, i.e.,within ±5 μm (±5 μm divided by 283 mm equals ±0.0018%) relative to thephotomask pattern.

EXAMPLE 3

A laminated member for a circuit board was obtained in the same manneras that in Example 1. Next, an edge of the polyimide film wasvacuum-sucked and the polyimide film was gradually peeled off the glasssubstrate. The resultant circuit board was left to stand in anatmosphere of 30° C. and 80% RH for one week, and bonding was attemptedby aligning an IC chip model that is similar to that in Example 1 withelectrode pads on the circuit board. Due to strain of the circuit board,in 4 units out of 49 units on the circuit board, it was not possible toalign the electrode pads on the circuit board with the bumps in the IC.

COMPARATIVE EXAMPLE 1

An adhesive for improving the adhesion of the metal layer was preparedin the same manner as that in Example 1. As in Example 1, the adhesivewas continuously applied to one surface of a long polyimide film(“UPILEX” manufactured by Ube Industries, Ltd.) with a thickness of 25μm and a width of 300 mm, followed by drying and curing.

On one of the surfaces of the polyimide film provided with the adhesivelayer, a chromium-nickel alloy layer with a thickness of 5 nm and acopper layer with a thickness of 200 nm were deposited in that order bya roll-to-roll type sputtering apparatus with a roll-to-roll system. Inthe alloy composition, the weight ratio of chromium to nickel was 20:80.

The polyimide film provided with the chromium-nickel alloy layer and thecopper layer was cut into a square sheet with a side of 300 mm. The cutpolyimide sheet was fixed by suction on the vacuum suction table, and apositive photoresist was applied to the copper layer, followed by dryingat 110° C. for 10 minutes. The photoresist was exposed through aphotomask and developed to form a resist layer with a thickness of 10 μmin the sections in which the plating layer was not required. In thephotomask pattern for testing, as in Example 1, one unit consisted of380 connecting pads (20 μm wide, 200 μm long) with a pitch of 50 μmarrayed in two parallel columns and a distance of 1.5 mm between thecenters of the adjacent pads, and respective units were uniformlyarrayed with a pitch of 40 mm in 7 rows and 7 columns on a squarepolyimide film with a side of 300 mm. At the same time, for the purposeof measuring length, 4 markers were provided on the photomask pattern atfour points diagonally apart from the center of the substrate with adistance of approximately 141 mm (the distance between the individualpoints being 200 mm in parallel to the side).

Using the copper layer as an electrode, a copper layer with a thicknessof 5 μm was formed by electroplating. A copper sulfate plating solutionwas used as the electroplating solution. The photoresist was removed bya photoresist stripper, and the copper layer and the chromium-nickelalloy layer below the resist layer were removed by soft etching using ahydrogen peroxide-sulfuric acid aqueous solution. In the same manner asthat in Example 1, a nickel layer with a thickness of 1 μm and a goldlayer with a thickness of 0.2 μm were deposited in that order on thecopper-plating layer. A metal layer pattern was thereby formed. Next, asin Example 1, a solder resist pattern was formed, and a circuit boardwas obtained.

The resultant circuit board was stored in an atmosphere of 25° C. and45% RH for 10 hours. The distance between the two points, which wereprovided for measuring length, originally about 283 mm apart diagonally(200 mm in the x direction, 200 mm in the y direction) was measured by alength-measuring device SMIC-800 (manufactured by Sokkia Co., Ltd.). Asa result, a deviation of 45 μm (45 μm divided by 283 mm equals 0.0159%)from the photomask pattern toward the outside of the board was observed,thus being a failure.

EXAMPLES 4 TO 8

In each Example, a laminated member for a circuit board was obtained inthe same manner as that in Example 1 except that the material for thereinforcing plate and the thickness of the reinforcing plate werechanged to those shown in Table 1.

After the resultant circuit board was stored in an atmosphere of 25° C.and 45% RH for 10 hours, the distance between the two points, which wereprovided for measuring length, originally about 283 mm apart diagonally(200 mm in the x direction, 200 mm in the y direction) was measured by alength-measuring device SMIC-800 (manufactured by Sokkia Co., Ltd.). Themaximum deviation from the photomask pattern measured is shown inTable 1. The measurement results in Example 1 are also shown in Table 1.In Example 6 in which a glass substrate was used as the reinforcingplate and the product of the Young's modulus and the cube of thethickness was less than 850 kg/mm, the maximum deviation of the circuitpattern was relatively satisfactory at 20 μm relative to 283 mm.However, the deviation is larger compared with Example 1, etc., whichmay result in a decrease in the yield in the fabrication of circuitsubstrates. TABLE 1 Thickness of Young's modulus Young's modulus ×Circuit pattern Circuit pattern Material for reinforcing of reinforcingcube of thickness maximum deviation dimensional change reinforcing plateplate (mm) plate (kg/mm²) (kg · mm) (μm) rate (%) Example 1Aluminoborosilicate 0.7 7,140 2,449 Within ±5 0.0018 or less glassExample 4 Soda glass 2 6,832 54,656 Within ±5 0.0018 or less Example 5Soda glass 0.5 6,832 854 10 0.0035 Example 6 Soda glass 0.4 6,832 437 200.0071 Example 7 Stainless steel 0.5 20,320 2,540 Within ±5 0.0018 orless Example 8 Stainless steel 0.05 20,320 2.5 17 0.0060

EXAMPLES 9 TO 15, COMPARATIVE EXAMPLE 2

As polyimide films, “UPILEX” (manufactured by Ube Industries, Ltd.)(Young's modulus: 930 kg/mm²) with a thickness of 25 μm, 75 μm, and 125μm, respectively, and “Kapton” (manufactured by DuPont-Toray Co.,Ltd.)(Young's modulus: 650 kg/mm²) with a thickness of 25 μm wereprepared.

In order to adjust the peeling strength between the polyimide film andthe adhesive, as an adhesive, a mixture of “Oribain” BPS5227-1(manufactured by Toyo Ink Mfg. Co., Ltd.) and a curing agent BXX5134(manufactured by Toyo Ink Mfg. Co., Ltd.) at a mixing ratio of 100:5 wasused in Example 9. In each of Example 10 and Example 11, a mixture of“Oribain” EXK01-257 (manufactured by Toyo Ink Mfg. Co., Ltd.) and acuring agent BXX5134 (manufactured by Toyo Ink Mfg. Co., Ltd.) at amixing ratio of 100:9 was used. In Example 12, a mixture of “Cyabain”SH-101 (manufactured by Toyo Ink Mfg. Co., Ltd.) and a curing agentT-501B (manufactured by Toyo Ink Mfg. Co., Ltd.) at a ratio of 100:3 wasused. In Example 13, a mixture of “SK-DYNE” SW-11A (manufactured bySoken Chemical and Engineering Co., Ltd.), a curing agent L45(manufactured by Soken Chemical and Engineering Co., Ltd.), and a curingagent E-5XM (manufactured by Soken Chemical and Engineering Co., Ltd.)at a mixing ratio of 100:2:0.7 was used. In Example 14, a mixture of“SK-DYNE” SW-11A (manufactured by Soken Chemical and Engineering Co.,Ltd.), a curing agent L45 (manufactured by Soken Chemical andEngineering Co., Ltd.), and a curing agent E-5XM (manufactured by SokenChemical and Engineering Co., Ltd.) at a mixing ratio of 100:3:1.5 wasused. In Example 15, a mixture of “Oribain” BPS5227-1 (manufactured byToyo Ink Mfg. Co., Ltd.) and a curing agent BXX5134 (manufactured byToyo Ink Mfg. Co., Ltd.) at a mixing ratio of 100:2 was used. InComparative Example 2, a mixture of “Oribain” BPS5673 (manufactured byToyo Ink Mfg. Co., Ltd.) and a curing agent BHS-8515 (manufactured byToyo Ink Mfg. Co., Ltd.) at a mixing ratio of 100:5 was used. The peelstrength of each adhesive is shown in Table 2. Data for Example 1 isalso shown in Table 2.

In each Example, a laminated member for a circuit board was obtained inthe same manner as that in Example 1 except that the adhesive describedabove was used. An edge of the polyimide film was vacuum-sucked and thepolyimide film was gradually peeled off the glass substrate. A circuitboard thus obtained was stored in an atmosphere of 25° C. and 45% RH for10 hours. The distance between the two points, which were provided formeasuring length, originally about 283 mm apart diagonally (200 mm inthe x direction, 200 mm in the y direction) was measured by alength-measuring device SMIC-800 manufactured by Sokkia Co., Ltd.). Themaximum deviation from the photomask pattern measured is shown in Table2.

The product A×B×C, i.e., the product of the peel strength A (g/cm), thereciprocal B (1/μm) of the thickness of the polyimide film, and thereciprocal C (mm²/kg) of the Young's modulus of the polyimide film, isshown in Table 2. If the product A×B×C was less than 4.3×10⁻⁶, since thepolyimide film was detached from the adhesive layer during the formationof the circuit pattern, the photoresist pattern was missing, resultingin a defect pattern. If the product A×B×C exceeded 4.3×10⁻³, thepolyimide film was extremely curled after peeling. The polyimide filmwas also deformed due to stress during peeling, resulting in a largedistortion in the circuit pattern on the polyimide film. TABLE 2Thickness of Young's modulus Circuit pattern Circuit pattern polyimidefilm of polyimide film Peel strength Appearance after maximum deviationdimensional change (1/B) (μm) (1/C) (kg/mm²) (A) (g/cm) A × B × Cpeeling (μm) rate (%) Example 1 25 930 2 8.60⁻⁵ Satisfactory Within ±50.0018 or less Example 9 25 930 15 6.45⁻⁴ Satisfactory Within ±5 0.0018or less Example 10 25 930 9 3.87⁻⁴ Satisfactory Within ±5 0.0018 or lessExample 11 25 650 9 5.54⁻⁴ Satisfactory 8 0.0028 Example 12 125 930 736.28⁻⁴ Satisfactory 13 0.0046 Example 13 75 930 1.2 1.72⁻⁵ Partiallydetached Within ±5 0.0018 or less in the process Example 14 25 930 0.083.44⁻⁶ Detached in the — Missing process pattern Example 15 25 930 572.45⁻³ Slightly curled 26 0.0092 Comparative 25 930 330 1.42⁻² Extremelycurled 130 0.0459 Example 2

EXAMPLES 16 TO 18

Laminated members for circuit boards were obtained in the same matter asthat in Example 1 except that the thickness of the self-stick, removableadhesive was set at 4.5 μm, 6 μm, and 15 μm, respectively. With respectto each member for a circuit board, while heating an IC chip model, inwhich 380 bumps plated with gold were arrayed with a pitch of 50 μm perone row and two rows were arrayed with a separation of 1.5 mm, at 150°C. from the chip side, using an ultrasonic bonder FC2000 (manufacturedby Toray Engineering Co., Ltd.), metal diffusion bonding with connectingpads on the circuit board was performed. The pressure for each bump was30 g. A cross section of the connecting part was taken and observed byan electron microscope to measure the sinking of the bump. The resultsthereof are shown in Table 3 below. Data in Example 1 is also shown inTable 3.

If the thickness of the self-stick, removable adhesive layer was 5 μm orless, the sinking of the bump was 6 μm or less, which caused no problemsin electrical connection reliability. On the other hand, if thethickness of the self-stick, removable adhesive layer exceeded 5 μm, thesinking of the bump exceeded 6 μm, resulting in a problem inreliability. TABLE 3 Thickness of adhesive layer Sinking (μm) (μm)Example 1 1 1.7 Example 16 4.5 5.8 Example 17 6 7.5 Example 18 15 13

EXAMPLE 19

A member for a circuit board was obtained in the same manner as that inExample 1 except that the auxiliary adhesive layer was not provided. Anedge of the polyimide film was vacuum-sucked and the polyimide film wasgradually peeled off the glass substrate. The self-stick, removableadhesive layer was partially detached from the glass and remained on thepolyimide film. After the polyimide film was peeled off, a step ofcleaning the polyimide film was required, resulting in a decrease inproductivity.

EXAMPLE 20

An adhesive for improving the adhesion of the metal layer was preparedin the same manner as that in Example 1. The adhesive was continuouslyapplied to a long polyimide film (“UPILEX” manufactured by UbeIndustries, Ltd.) with a thickness of 25 μm and a width of 300 mm,followed by drying and curing. Similarly, the adhesive was applied tothe other surface of the polyimide film, followed by drying and curing.

As an auxiliary adhesive, γ-aminopropyltriethoxy silane was dissolved inisopropyl alcohol so as to obtain a concentration of 5% by weight. Theauxiliary adhesive solution was applied by a spin coater to a squaresoda glass with a side of 300 mm and a thickness of 0.5 mm, followed bydrying at 100° C. for 5 minutes. The dried auxiliary adhesive layer hada thickness of 300 nm. A mixture obtained by mixing an acrylic adhesive“SK-DYNE” SW-11A (manufactured by Soken Chemical and Engineering Co.,Ltd.), in which adhesion was decreased by ultraviolet curing, with acuring agent L45 (manufactured by Soken Chemical and Engineering Co.,Ltd.) at a mixing ratio of 50:1 was applied to the glass substrateprovided with the auxiliary adhesive layer, followed by drying at 80° C.for 2 minutes. The dried adhesive layer had a thickness of 1 μm. Twoglass substrates provided with the auxiliary adhesive layers and theself-stick, removable adhesive layers were prepared. Next, anair-shielding film composed of a film in which an easily releasablesilicone resin layer was placed on a polyester film was attached to theadhesive layer and was left to stand for one week. The glass substratehad a Young's modulus of 6,832 kg/mm², and the product of the Young'smodulus (kg/mm²) and the cube of the thickness (mm) was 854 kg·mm.

The polyimide film on which the adhesive for improving the adhesion ofthe metal layer was coated was cut into a square with a side of 300 mmand was stored in an atmosphere of 25° C. and 45% RH for 10 hours. Next,in the same manner as that in Example 1, the polyimide film providedwith the adhesive layer was laminated to the first glass substrateprovided with the self-stick, removable adhesive layer. The glasssubstrate to which the polyimide film was laminated was removed from thestage, and the adhesive layer was cured by ultraviolet irradiation at1,000 mJ/cm² from the glass substrate side.

On the polyimide film laminated on the glass substrate, achromium-nickel alloy layer with a thickness of 4 nm and a copper layerwith a thickness of 200 nm were deposited in that order by sputtering.In the alloy composition, the weight ratio of chromium to nickel was20:80.

A positive photoresist was applied to the copper layer by a spin coaterand dried at 110° C. for ten minutes. The photoresist was exposedthrough a photomask. Next, the photoresist was developed, and a resistlayer with a thickness of 10 μm was thereby formed in the sections whichdid not require a plating layer. Four markers were provided on thephotomask pattern at four points diagonally apart from the center of thesubstrate with a distance of approximately 141 mm (the distance betweenthe individual points being 200 mm in parallel to the side).

Next, using the copper layer as an electrode, a copper layer with athickness of 5 μm was formed by electroplating. A copper sulfate platingsolution was used as the electroplating solution. The photoresist wasremoved by a photoresist stripper, and the copper layer and thechromium-nickel alloy layer below the resist layer were removed by softetching using a hydrogen peroxide-sulfuric acid aqueous solution.

The distance between the two points, which were provided for measuringlength as described above, originally about 283 mm apart diagonally (200mm in the x direction, 200 mm in the y direction) was measured by alength-measuring device SMIC-800 (manufactured by Sokkia Co., Ltd.). Asa result, dimensional change rate was extremely satisfactory, i.e.,within ±5 μm (±5 μm divided by 283 mm equals ±0.0018%) relative to thephotomask pattern.

After the air-shielding film was removed from the second glass substrateprovided with the auxiliary adhesive layer and the self-stick, removableadhesive layer, the polyimide film provided with the copper layerpattern was placed thereon, and both were laminated with each other bypassing them through a roll laminator MAII-550 (manufactured by TaiseiLaminator Co., Ltd.). Both the upper roller and the lower roller weremetal rollers coated with rubber. The rubber hardness of the upperroller was Hs50, and the rubber hardness of the lower roller was Hs70.

The surface of the second glass substrate was fixed on a vacuum suctiontable, and an edge of the first glass substrate was vacuum-sucked andthe first glass substrate was gradually peeled off. After the firstglass substrate was removed, the second glass substrate was detachedfrom the vacuum suction table, and the adhesive layer was cured byultraviolet irradiation at 1,000 mJ/cm² from the glass substrate side.

On the polyimide film laminated on the glass substrate, achromium-nickel alloy layer with a thickness of 4 nm and a copper layerwith a thickness of 200 nm were deposited in that order by sputtering.In the alloy composition, the weight ratio of chromium to nickel was20:80.

A positive photoresist was applied to the copper layer by a spin coaterand dried at 110° C. for ten minutes. The photoresist was exposedthrough a photomask. Next, the photoresist was developed, and a resistlayer with a thickness of 10 μm was thereby formed in the sections whichdid not require a plating layer. Four markers were provided on thephotomask pattern at four points diagonally apart from the center of thesubstrate with a distance of approximately 141 mm (the distance betweenthe individual points being 200 mm in parallel to the side).

Next, using the copper layer as an electrode, a copper layer with athickness of 5 μm was formed by electroplating. A copper sulfate platingsolution was used as the electroplating solution. The photoresist wasremoved by a photoresist stripper, and the copper layer and thechromium-nickel alloy layer below the resist layer were removed by softetching using a hydrogen peroxide-sulfuric acid aqueous solution.

The distance between the two points, which were provided for measuringlength as described above, originally about 283 mm apart diagonally (200mm in the x direction, 200 mm in the y direction) was measured by alength-measuring device SMIC-800 (manufactured by Sokkia Co., Ltd.). Asa result, dimensional change rate was extremely satisfactory, i.e.,within ±5 μm (±5 μm divided by 283 mm equals ±0.0018%) relative to thephotomask pattern.

An edge of the polyimide film was vacuum-sucked and the polyimide filmwas gradually peeled off the glass substrate to obtain a circuit board.The resultant circuit board was stored in an atmosphere of 25° C. and45% RH for 10 hours. The distance between the two points, which wereprovided for measuring length, originally about 283 mm apart diagonally(200 mm in the x direction, 200 mm in the y direction) was measured bythe length-measuring device SMIC-800. As a result, dimensional changerate was maintained extremely satisfactorily, i.e., within ±5 μm (±5 μmdivided by 283 mm equals ±0.0018%) relative to the photomask pattern.

COMPARATIVE EXAMPLE 3

A laminated member for a circuit board was fabricated in the same manneras that in Example 1 except that, instead of curing the adhesive layerby ultraviolet irradiation from the glass substrate side, after thepolyimide film was laminated to the glass substrate, ultravioletirradiation was performed immediately before the application of thesolder resist. When the photoresist applied on the copper layer wasdried, foaming occurred in the adhesive layer, resulting inirregularities on the surface of the polyimide film. In the wet process,the self-stick, removable adhesive layer swelled and the holding powerfor holding the polyimide film was decreased. Therefore, when thedistance between the two points, which were provided for measuringlength, originally about 283 mm apart diagonally (200 mm in the xdirection, 200 mm in the y direction) was measured by thelength-measuring device SMIC-800, a maximum deviation of 80 μm (80 μmdivided by 283 mm equals 0.028%) from the photomask pattern was found.

When the polyimide film of the resultant laminated member for thecircuit board was peeled from the glass substrate, the peel strength was40 g/cm, which was larger than that in Example 1, and the circuitsubstrate after peeling was slightly curled. The product A×B×C, i.e.,the product of the peel strength A (g/cm), the reciprocal B (1/μm) ofthe thickness of the polyimide film, and the reciprocal C (mm²/kg) ofthe Young's modulus of the polyimide film, was 1.72×10⁻³.

COMPARATIVE EXAMPLE 4

A laminated member for a circuit board was obtained in the same manneras that in Example 1 except that a roll laminator was used when thepolyimide film was laminated to the glass substrate provided with theself-stick, removable adhesive layer. As the roll laminator, MAII-550(manufactured by Taisei Laminator Co., Ltd.) was used. Both the upperroller and the lower roller were metal rollers coated with rubber. Therubber hardness of the upper roller was Hs50, and the rubber hardness ofthe lower roller was Hs70.

An edge of the polyimide film was vacuum-sucked and the polyimide filmwas gradually peeled off the glass substrate. A circuit board wasthereby obtained. The resultant circuit board was stored in anatmosphere of 25° C. and 45% RH for 10 hours. The distance between thetwo points, which were provided for measuring length, originally about283 mm apart diagonally (200 mm in the x direction, 200 mm in the ydirection) was measured by the length-measuring device SMIC-800. As aresult, the polyimide film was deformed due to stress applied duringlamination. Expansion occurred in the roller passage direction andshrinkage occurred in a direction perpendicular to the roller passagedirection. That is, stress in the polyimide film was released by thepeeling of the polyimide film, and strain occurred in the circuitpattern on the polyimide film. The maximum strain was 100 μm (100 μmdivided by 283 mm equals 0.035%) relative to the photomask pattern.

EXAMPLE 21

A laminated member for a circuit board was obtained in the same manneras that in Example 1 except that the following method was employed whenthe polyimide film was laminated to the glass substrate provided withthe self-stick, removable adhesive layer.

A polyimide film 4 provided with a self-stick, removable adhesive layer,cut into a square with a side of 300 mm was placed on the stage 3provided with a vacuum suction mechanism shown in FIG. 3, and vacuumsuction was performed. Water was then sprayed onto the polyimide film bya nozzle (not shown in the drawing). A 100-mesh screen gauze 2 composedof polyester fibers was placed so as to face the polyimide film 5 inparallel with a separation of 0.7 mm therebetween. The surface of thescreen gauze 2 opposite to the surface abutting on the polyimide filmwas squeegeed by a rubber plate 8, and while decreasing the thickness ofthe water film between the polyimide film 4 and the screen gauze 2, thescreen gauze 2 and the polyimide film 4 were brought into close contactwith each other. The vacuum suction of the stage 3 was stopped, thescreen gauze was moved upward, and the polyimide film 4 was transferredto the screen gauze 2. The openings of the screen gauze were placedinside the region which was laminated to the polyimide film by 2 mm sothat excess water did not spread over the stage.

The glass substrate 6 provided with the self-stick, removable adhesivelayer 7 was placed on the stage 3 provided with the vacuum suctionmechanism. The screen gauze 2 laminated with the polyimide film 4 wasmoved to the position above the glass substrate 6.

The screen gauze 2 was moved downward and placed above the glasssubstrate with a separation of 0.7 mm. Next, the surface of the screengauze 2 opposite to the surface abutting on the polyimide film wassqueegeed by a rubber plate 8 with a Shore hardness of 50 to press thepolyimide film 4 against the self-stick, removable adhesive layer 7, andthe polyimide film 4 was thereby transferred to the glass substrate.

An edge of the polyimide film was vacuum-sucked and the polyimide filmwas gradually peeled off the glass substrate. A circuit board wasthereby obtained. The resultant circuit board was stored in anatmosphere of 25° C. and 45% RH for 10 hours. The distance between thetwo points, which were provided for measuring length, originally about283 mm apart diagonally (200 mm in the x direction, 200 mm in the ydirection) was measured by the length-measuring device SMIC-800. As aresult, dimensional change rate was maintained extremely satisfactorily,i.e., within ±5 μm (±5 μm divided by 283 mm equals ±0.0018%) relative tothe photomask pattern.

EXAMPLE 22

A laminated member for a circuit board was obtained in the same manneras that in Example 1 except that the following method was employed whenthe polyimide film was laminated to the glass substrate provided withthe adhesive layer.

An emulsion was applied over the entire surface to a 100-mesh screengauze 2 composed of polyester filaments to seal the openings. Byscreen-printing the same material as that for the self-stick, removableadhesive layer provided on the glass substrate, dot-shaped adhesiveparts were formed on the screen gauze 2. The dot had a diameter of 0.5mm, and the distance between the adjacent dots was 5 mm. The dots wereuniformly placed on the screen gauze at the surface abutting on thepolyimide film.

A polyimide film 4 was cut into a square with a side of 300 mm on whichan adhesive was deposited, and was placed on stage 3 provided with avacuum suction mechanism shown in FIG. 3, and vacuum suction wasperformed. The screen gauze 2 provided with the dot-shaped adhesiveparts was placed so as to face the polyimide film 4 in parallel. Thescreen gauze 2 was moved downward so as to face the polyimide film 4 inparallel with a separation of 0.7 mm. The surface of the screen gauze 2opposite to the surface abutting on the polyimide film was squeegeed bya rubber plate 8, and the screen gauze 2 and the polyimide film 4 werebrought into close contact with each other. The vacuum suction of thestage 3 was stopped, the screen gauze 2 was moved upward, and thepolyimide film 4 was transferred to the screen gauze 2.

The glass substrate 6 provided with the self-stick, removable adhesivelayer 7 was placed on the stage 3 provided with the vacuum suctionmechanism. The screen gauze 2 laminated with the polyimide film 4 wasmoved downward and placed parallel to the glass substrate 6 with aseparation of 0.7 mm. Next, the surface of the screen gauze 2 oppositeto the surface abutting on the polyimide film was squeegeed by therubber plate 8 to press the polyimide film 4 against the self-stick,removable adhesive layer 7, and the polyimide film 4 was therebytransferred to the glass substrate.

An edge of the polyimide film was vacuum-sucked and the polyimide filmwas gradually peeled off the glass substrate. A circuit board wasthereby obtained. The resultant circuit board was stored in anatmosphere of 25° C. and 45% RH for 10 hours. The distance between thetwo points, which were provided for measuring length, originally about283 mm apart diagonally (200 mm in the x direction, 200 mm in the ydirection) was measured by the length-measuring device SMIC-800. As aresult, dimensional change rate was maintained extremely satisfactorily,i.e., within ±5 μm (±5 μm divided by 283 mm equals ±0.0018%) relative tothe photomask pattern.

INDUSTRIAL APPLICABILITY

The circuit boards of the present invention are favorably used forwiring boards for electronic apparatuses, interposers for IC packaging,wiring boards for wafer level burn-in sockets, and the like.

1. A method for making a laminated member for a circuit board comprisingthe steps of laminating a flexible film to a reinforcing plate, andforming a circuit pattern comprising a metal on the flexible film.
 2. Amethod for making a circuit board comprising the steps of laminating aflexible film to a reinforcing plate, forming a circuit patterncomprising a metal on the flexible film, and peeling the flexible filmoff the reinforcing plate.
 3. A method for making a circuit boardaccording to claim 2, wherein a first circuit pattern is formed on afirst surface of the flexible film, the reinforcing plate and the firstsurface of the flexible film are laminated to each other with aself-stick, removable organic layer therebetween, and a second circuitpattern is formed on a second surface of the flexible film.
 4. A methodfor making a circuit board according to claim 2, wherein a firstreinforcing plate and the flexible film are laminated to each other witha self-stick, removable organic layer therebetween, a first pattern isformed on a first surface of the flexible film, the first surface and asecond reinforcing plate are laminated to each other with a self-stick,removable organic layer therebetween, the flexible film is peeled offthe first reinforcing plate, a second circuit pattern is formed on asecond surface of the flexible film, and the flexible film is peeled offthe second reinforcing plate.
 5. A method for making a circuit boardaccording to claim 2, wherein the flexible film is peeled off thereinforcing plate after electronic components are further bonded ontothe circuit pattern composed of the metal.
 6. A method for making acircuit board according to claim 2, wherein a via hole is formed from asurface of the flexible film opposite to the surface laminated to thereinforcing plate.
 7. A method for making a circuit board according toclaim 2, wherein the reinforcing plate is a sheet.
 8. A method formaking a circuit board according to claim 2, further comprising a stepof irradiating an ultraviolet curable, self-stick, removable organiclayer with ultraviolet light before the step of forming the circuitpattern.
 9. A method for making a circuit board according to claim 2,wherein the flexible film is held on a surface of a film holding sheet,the flexible film is placed so as to face a surface of the reinforcingplate provided with a self-stick, removable organic layer at apredetermined distance, and the flexible film is transferred to thereinforcing plate by pressing the film holding sheet and the flexiblefilm against the reinforcing plate.
 10. A method for laminating aflexible film according to claim 9, wherein the film holding sheet andthe flexible film are pressed against the reinforcing plate by moving alinear pressing element from one edge to the other edge of the flexiblefilm.
 11. A method for laminating a flexible film according to claim 9,wherein the flexible film is held on the surface of the film holdingsheet using surface tension of a liquid, electrostatic adsorption, oradhesion of an organic substance.